high PH and high TA

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
noreen

high PH and high TA

Postby noreen » Fri 01 Sep, 2006 10:12

I have been trying to lower my ph with sodium bisulfurate but my TA is very high - around 200 ppm. My test kits also say that my chlorine is very low.

My pool is crystal clear and I have been having these high readings for a while.

Any idea for next steps.

Thanks.

Noreen


Guest

Re: high PH and high TA

Postby Guest » Fri 01 Sep, 2006 13:20

noreen wrote:I have been trying to lower my ph with sodium bisulfurate but my TA is very high - around 200 ppm. My test kits also say that my chlorine is very low.

My pool is crystal clear and I have been having these high readings for a while.

Any idea for next steps.

Thanks.

Noreen

Yes, with an alkalinity level that high the pH has a strong tendency to drift upwards. And with a high ph you *may* get cloudy water and deposits along the water line. The low chlorine is an altogether different matter, you may need to simply add chlorine and/or stabilizer.

One option is (a) lower the pH to about 7.0 (b) set the return eyeball so there is some turbulence created when the water is expelled (c) keep monitoring the pH and keep it at 7.0 all the time. This process will lower your alkalinity but it won't be instantaneous, it'll take a few days. If you have a fountain you can use that for greater effect. Note that the water temperature may drop if you aerate.

(By lowering th pH to a lower level this shifts the alcalinity components to predominantly carbon dioxide and the aeration removes the carbon dioxide. By removing the carbon dioxide the pH rises so that's why you have to keep an eye on it and keep it low. The more aeration you get going the faster process it becomes. If you don't aerate the water will naturally outgas CO2 but at a much slower rate, and you'll use up more bisulfate.)

You can illustrate the process by taking a tablespoon of baking soda (remember you add baking soda to raise alkalinity in swimming pools) and spraying vinegar on it (vinegar's an acid, just like the bisulfate). You'll see CO2 being expelled. You're doing the same thing to your pool but on a different scale.

Oh and that's why Coke and other soft drinks have low pH, it's not the beverage, it's the carbon dioxide.

The other option out there involves slugging muriatic acid (or dissolved sodium bisulfate in a bucket), that is, pour the product in a small area slowly, always at the same spot. It is said that the acid concentration caused by this acid pocket eventually breaks the alkalinity buffering. Be careful when you handle muriatic acid or dissolved bisulfate.

The other other option is to leave things as is, you may need to set other parameters (like pH and calcium hardness) in order to get 'balanced' water (neither scaling nor corrosive). For this you can ask our friend Google about the Langelier Saturation Index. Depending on your geographical location (your temperature, and if you're about to winterize the pool in a couple of months) it may be the simplest thing to do until you close your pool (if you do).

For the chlorine you may just need to add some. Make sure you have enough of a chlorine residual to prevent any algae from moving in. The proper level of chlorine residual (and the chlorine effectiveness) is a function of pH and stabilizer level. The lower the pH the more effective chlorine becomes, the more stabilizer in the water the less effective chlorine becomes. People usually start getting into problems when the stabilizer levels reaches 100 ppm.

Whatever you decide to do, please be careful in handling and storing the chemicals and absolutely never ever mix the bisulfate/acid and the chlorine in the same container. This is no joke.

Best regards,

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